unifpdf_2d.m

%unifpdf_2d
%Last modified 21 November 2013
%Matlab code by Bryan Clarke b.clarke@acfr.usyd.edu.au 

%A 2D uniform PDF function. 
%xrange and yrange are inclusive limits of region
%z is a 2D sample point.
%This is used in the clutter function (i.e. we assume a uniform
%distribution of clutter). 
%This implementation is fairly standard for a uniform distribution in X and
%Y. This can be problematic for our application if care is not taken.
%With a uniform distribution, we assume there is ZERO probability outside of the region of interest.
%This implies that any measurement outside the region of interest has ZERO probability of
%clutter, when it should have 100% probability of clutter (i.e. we cannot make good measurements 
%outside that region).
%For this implementation we never have any measurements outside the region
%of interest, and the state estimates are never predicted/updated outside of that region
%but this might not be the case with other simulations or actual data. BEWARE!
function val = unifpdf_2d(xrange, yrange, z)
    minX = xrange(1);
    maxX = xrange(2);
    minY = yrange(1);
    maxY = yrange(2);
    evalX = z(1);
    evalY = z(2);
    if(evalX < minX)
        val = 0;
        return;
    elseif(evalX > maxX)
        val = 0;
        return
    elseif (evalY < minY)
        val = 0;
        return;
    elseif(evalY > maxY)
        val = 0;
        return;
    else
        val = 1 / ((maxX - minX) * (maxY - minY));
    end

end